Steel vs aluminium scaff tubes

This fine (steel) specimen was still surprisingly strong when it came out of the entrance to Malham Cove Rising, after corroding quietly for almost 5 decades.
MCR_FR_new_31.jpeg
 
30 years was for scaff in damp location, dry it can last a lot longer, or running water with added minerals may shorten it's life
 
mikem said:
Usually as solid as it looks - same principle as karabiners don't particularly have a shelf life whilst plastics and fabrics (harnesses and ropes) do. Ball park figure I heard is good for 30 years underground, whilst treated railway sleepers nearer 100
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Not sure if true, but I think old railway sleepers from 1990s or before have a much longer lifespan than newer old railway sleepers. I was told not to use them for e.g. raised vegetable beds or anything much in the garden as whatever they treated them with was effective but nasty.
 
Aluminium alloy corrodes less than steel, but some caves may have more aggressive condition. I took a brand new shiny krab down F'ing Hopeless and it came out looking 10 years old.
 
ChrisB said:
Aluminium alloy corrodes less than steel, but some caves may have more aggressive condition. I took a brand new shiny krab down F'ing Hopeless and it came out looking 10 years old.
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Typical aluminium alloys or pure aluminium has good corrosion resistance, but the high strength alloy used in carabiners has copper added which significantly reduces their corrosion resistance.
 
If used as a beam would it be accurate enough as a comparison to support the ends on a flat surface and load the mid point and measure the deflection with a ruler on both samples (the weight could be 1 or 2 cavers)
 
Assuming the geometry is the same for each one, your deflection test would just compare the stiffness of the two tubes (related to Youngs Modulus and wall thickness).

For the load capacity, the load at which it would fail in bending is related to the wall thickness and yield strength (permanent bend) and ultimate tensile strength (total failure).

Dependant on the alloys of both steel and aluminium and how they are work hardened or heat treated, it is possible to have widely varying yield strengths in either material. Soft, ductile all the way through to hard and brittle. Resistance to crack propagation (toughness) can also be varied. Even the sides, top and ring pull of a coke can have different alloys because they need to do different jobs.

The stiffness (and hence deflection) of aluminium or steel is largely unaffected by how they are alloyed or treated. Steel being about 3x as stiff.

So your test is useful for proving it doesn’t just collapse under two (or more cavers), the deflection itself isn’t that useful as an indicator.
 
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